U.S. patent application number 16/759841 was filed with the patent office on 2021-06-17 for method for the functional testing of an electromechanical fill level monitoring device.
The applicant listed for this patent is Robert Bosch GmbH. Invention is credited to Ralf Kinder, Matthias Kistner, Klaus Walter, Peter Ziegler.
Application Number | 20210179043 16/759841 |
Document ID | / |
Family ID | 1000005431776 |
Filed Date | 2021-06-17 |
United States Patent
Application |
20210179043 |
Kind Code |
A1 |
Walter; Klaus ; et
al. |
June 17, 2021 |
METHOD FOR THE FUNCTIONAL TESTING OF AN ELECTROMECHANICAL FILL
LEVEL MONITORING DEVICE
Abstract
A method for functional testing of an electromechanical fill
level monitoring device. In order to test the plausibility of a
signal emitted by a fill level monitoring device of a first
pressure medium chamber, a forced actuation of this fill level
monitoring device is carried from time to time. This forced
actuation is carried out in that a pressure medium delivery unit in
a pressure medium circuit having the first pressure medium chamber
is activated for a predefined period. This delivers the pressure
medium fill level monitoring device into a second pressure medium
chamber via a pressure medium connection. On the basis of the
signal profile output by the fill level monitoring device, the
proper operation of the fill level monitoring device is inferred in
the electronic control unit.
Inventors: |
Walter; Klaus;
(Bietigheim-Bissingen, DE) ; Ziegler; Peter;
(Grossbottwar, DE) ; Kistner; Matthias;
(Bretzfeld, DE) ; Kinder; Ralf; (Auenstein,
DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Robert Bosch GmbH |
Stuttgart |
|
DE |
|
|
Family ID: |
1000005431776 |
Appl. No.: |
16/759841 |
Filed: |
September 20, 2018 |
PCT Filed: |
September 20, 2018 |
PCT NO: |
PCT/EP2018/075428 |
371 Date: |
April 28, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B60T 8/4081 20130101;
B60T 13/745 20130101; B60T 7/042 20130101; B60T 17/225 20130101;
B60T 13/686 20130101; B60T 13/146 20130101; B60T 13/662
20130101 |
International
Class: |
B60T 8/40 20060101
B60T008/40; B60T 17/22 20060101 B60T017/22; B60T 13/66 20060101
B60T013/66; B60T 13/14 20060101 B60T013/14; B60T 13/74 20060101
B60T013/74; B60T 13/68 20060101 B60T013/68; B60T 7/04 20060101
B60T007/04 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 30, 2017 |
DE |
102017221478.3 |
Claims
1-5. (canceled)
6. A method for functional testing of an electromechanical fill
level monitoring device in a first pressure medium chamber of a
pressure medium circuit whose pressure is regulated using an
electronic control unit, the pressure medium circuit including at
least one second pressure medium chamber separated from the first
pressure medium chamber, the first pressure medium chamber and the
second medium chamber being connected to each other by a pressure
medium connection, the pressure medium circuit further including an
electronically activatable pressure medium delivery unit situated
in the pressure medium connection between the first and second
pressure medium chambers, the method comprising the following
steps: activating the pressure medium delivery unit over an
established period to deliver pressure medium contained in the
first pressure medium chamber into the second pressure medium
chamber; detecting and evaluating, by the electronic control unit,
a signal profile of the fill level monitoring device within the
established period; and emitting a warning signal by the electronic
control unit when no signal jump or no continuous signal change is
detected in the signal profile within the established period.
7. The method as recited in claim 6, wherein the pressure medium
circuit is a brake circuit of an electronic slip-controllable
vehicle braking system.
8. The method as recited in claim 6, wherein the output of a
warning signal is suppressed when a signal jump or a continuous
signal change is detected in the signal profile by the electronic
control unit.
9. The method as recited in claim 6, wherein the method is carried
out at regularly recurring intervals.
10. The method as recited in claim 6, wherein the method is carried
out during a startup of a drive of the vehicle.
11. The method as recited in claim 6, wherein the pressure medium
circuit is a brake circuit of an electronic slip-controllable
vehicle braking system which is equipped with a master brake
cylinder, a wheel brake, an electronically activatable circuit
separating valve between the master brake cylinder and the wheel
brake, and an electronically activatable check valve between the
pressure generator and the wheel brake, and wherein the check valve
and the circuit separating valve are activated by the electronic
control unit to carry out the method in such a way that the check
valve and the circuit separate valve are each in a passage
position.
12. The method as recited in claim 6, where first and second
pressure medium chambers communicate the pressure medium with one
another via an equalization opening, wherein, after the expiration
of the established period, a time is measured by the electronic
control unit until a signal of the fill level monitoring device
assumes a value that was present at a beginning of the established
period, and a quality of the pressure medium is judged by the
electronic control unit from the measured time.
Description
FIELD
[0001] The present invention is directed to a method for the
functional testing of an electromechanical fill level
monitoring.
BACKGROUND INFORMATION
[0002] Fill level monitoring devices have been installed in motor
vehicles for many years, in order to promptly detect a low level of
brake fluid in a brake fluid reservoir and, if necessary, display
this to a driver.
[0003] For this purpose, conventional fill level monitoring devices
have a float gauge situated in the brake fluid reservoir, which
carries a magnet. This float gauge moves, depending on the fill
level of the brake fluid reservoir, on a sensor element equipped
with a switch contact, for example, a reed contact. As soon as the
fill level drops below a minimum mark, a switching operation is
triggered by the magnet in the sensor element, which causes a
warning signal to be emitted to a driver by an electronic control
unit. Visual, acoustic, and/or haptic signals are customary as
warning signals.
[0004] Continuously acting fill level monitoring devices are also
conventional. These have a potentiometer actuated by the float
gauge, whose resistance changes depending on the float gauge
position and thus of the fill level of the brake fluid
reservoir.
[0005] Under normal operating conditions, the fluid level in a
pressure medium chamber is above the aforementioned minimum mark
over the long term and the float gauge moves only within a
relatively small displacement range. As a consequence, no switching
operation is triggered at the switch contact or no resistance
change is triggered at the potentiometer, and the fill level
monitoring device appropriately emits a signal which represents the
sufficiently high fill level.
[0006] However, in the case that the float gauge is, for example,
mechanically blocked, and therefore a potential fill level drop may
no longer be detected, or if the sensor element has stalled
contacts, then a fill level, which has dropped below the minimum
volume, may no longer be easily detected, and the warning signal to
the driver fails to appear.
[0007] In an extreme case, gas from the atmosphere might thus
penetrate into the hydraulic circuit, or ultimately the build-up of
brake pressure by a pressure generator might be compromised,
without this having been noticed. This is particularly critical in
so-called power brake systems, which buildup brake pressure
independently from the driver and are additionally configured as
open systems, i.e., as braking systems whose brake pressure
generator is supplied with pressure medium directly from a pressure
medium chamber of a reservoir.
SUMMARY
[0008] Using an example method of the present invention for
functional testing of an electromechanical fill level monitoring
device prevents functional failures of this fill level monitoring
device from remaining undetected for longer periods.
[0009] According to an example embodiment of a method in accordance
with the present invention, a response of the brake fluid switch is
provoked by a targeted reduction of the fill level of a first
pressure medium chamber equipped with a fill level monitoring
device, and the signal profile thereby emitted is observed by the
fill level monitoring device. If, in the observation period, a
signal jump or at least a continuous signal change occurs,
depending on the functional principle of a sensor of the fill level
monitoring device, it may be inferred that the fill level
monitoring device is functioning properly and the output of a
warning signal may be suppressed in the control unit, while a lack
of a signal jump or an inconsistent or discontinuous signal change
may be interpreted as an error function of the fill level
monitoring device and triggers such a warning signal.
[0010] The method may then always be carried out when no pressure
medium delivery takes place in the hydraulic circuit, thus when the
pressure medium delivery device is not activated or actuated for
brake pressure generation. In a motor vehicle, the method may be
routinely carried out, for example, always after a start of the
vehicle drive or after starting up the vehicle following an idle
phase.
[0011] The aforementioned drop of the fill level in a first
pressure medium chamber may be carried out on the basis of a
pressure medium delivery device, which is usually present in a
hydraulic circuit anyway. In particular, brake circuits of
electronically slip-controllable vehicle braking systems are
equipped with pressure generators or pressure medium delivery
devices, which may be used for this purpose. In addition, only
minor additional modifications are necessary at these types of
brake circuits in order to be able to carry out the described
method. For example, a second pressure medium chamber is provided,
into which the pressure medium may be pumped from the first
pressure medium chamber.
[0012] The two pressure medium chambers should advantageously be in
permanent communication with one another via an equalizing opening
of a known cross-sectional area. The circulated pressure medium may
thus automatically, i.e., without pump assistance, flow back into
the first pressure medium chamber via the equalizing opening,
further information regarding temperature, viscosity, and/or degree
of contamination, thus the quality, of the pressure medium being
obtained from a measurable duration of the return flow of the
pressure medium, and may be taken into consideration in regulating
the brake pressure in the brake circuit. Particularly advantageous
in this regard are reservoirs for pressure medium, which are
divided into two pressure medium chambers communicating with one
another, since they may already be inexpensively obtained on the
market.
[0013] Additional advantages or advantageous refinements of the
method underlying the present invention arise from the description
below and the figures.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] An exemplary embodiment of the present invention is
described in greater detail in the subsequent description and
illustrated on the basis of the figures.
[0015] FIG. 1 shows the hydraulic layout of an electronic
slip-controllable power braking system of a motor vehicle.
[0016] FIG. 2 shows a schematically simple pressure medium
circuit.
[0017] FIG. 3 shows an example method underlying the present
invention on the basis of a flow chart.
DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS
[0018] FIG. 1 shows by way of example the hydraulic layout of a
vehicle braking system 110. This vehicle braking system 110 is a
power braking system, thus a vehicle braking system in which the
brake pressure at the wheel brakes 112 is not provided by the
muscle force of the driver in problem-free normal operation, but
instead by a pressure generator 114, which is equipped to be
drivable by an electric motor. Depicted vehicle braking system 110
includes a master brake cylinder 118, which is actuatable by the
driver via braking pedal 116 and to which two brake circuits 120,
122 are connected. Both brake circuits 120, 122 each supply two
assigned wheel brakes 112 with pressure medium. On the basis of
master brake cylinder 118, a braking intent of the driver is merely
detected under normal operations; only in the case of present
malfunctions may the driver apply brake pressure to the wheel
brakes 112 via master brake cylinder 118. During standard operation
of vehicle braking system 110, brake pressure is therefore applied
to wheel brakes 112 using a pressure generator 114. This pressure
generator 114 is hydraulically switched in parallel to master brake
cylinder 118. Pressure generator 114 is a plunger piston 124, which
may be driven to an axial motion in a cylinder 128 by an
electrically activatable drive motor 126. A rotary motion of drive
motor 126 is thereby converted with the aid of a spindle drive into
an axial motion and transmitted to plunger piston 124. The pressure
medium supplied by plunger piston 124 is displaced into brake
circuits 120, 122 and thus causes a buildup of brake pressure.
Brake circuits 120, 122 may be separated if necessary from plunger
piston 124 via check valves 130, these check valves 130 being
designed to be electronically activatable. For an individual wheel
adjustment of the brake pressure to the slip ratio prevailing at an
assigned wheel, a modulation device, made from an electronically
activatable pressure build-up valve 132 and a likewise
electronically activatable pressure reduction valve 134, is
connected upstream or downstream. In addition, a circuit separating
valve 136 is provided in each of the brake circuits 120, 122. This
circuit separating valve 136 is likewise designed to be
electronically controllable and blocks a pressure medium connection
between master brake cylinder 118 and brake circuits 120, 122 under
normal conditions to prevent a buildup of brake pressure therein
via master brake cylinder 118.
[0019] Vehicle braking system 110 is additionally equipped with a
pedal travel simulator 138. This is a piston/cylinder unit, which
is controllable with the aid of a simulator decoupling valve 156
and may be coupled to one of the chambers of master brake cylinder
118. Pedal travel simulator 138 receives pressure medium displaced
from master brake cylinder 118 when the pressure medium connection
from master brake cylinder 118 to brake circuits 120, 122 is
blocked by circuit separating valve 136 and then facilitates a
pedal travel to brake pedal 116, actuated by the driver and acted
upon by master brake cylinder 118. Pedal sensors 140 at brake pedal
116 detect this pedal travel and convert the travel signal into a
voltage signal which they provide to an electronic control unit 142
of vehicle braking system 110. A braking intent of the driver is
recognized in electronic control unit 142 on the basis of this
signal and converted into a control signal, with which electronic
control unit 142 activates pressure generator 114 or its drive
motor 126. This then introduces a brake pressure at wheel brakes
112 corresponding to the actuation of brake pedal 116.
[0020] The chambers of the master brake cylinder assigned to
respective brake circuits 120, 122 are supplied with pressure
medium via a pressure medium reservoir 144. That pressure medium
reservoir 144 is divided into multiple chambers 146, 148, 150 which
communicate with one another. Each single chamber 146, 148 is
respectively assigned to one of brake circuits 120, 122; a third
chamber 150 is directly connected to pressure generator 114.
[0021] It is assumed that aforementioned pressure medium reservoir
144 is equipped with a fill level monitoring device, which emits a
warning signal as intended when the fill level drops below a
predefined minimum value. Furthermore, it is assumed that this fill
level monitoring device is situated in third chamber 150 of
pressure medium reservoir 144 connected to pressure generator
114.
[0022] Pressure generator 114 is activated according to the present
invention to check the functionality of this fill level monitoring
device. Pressure generator 114 therefore displaces the pressure
medium present in its cylinder 128 through correspondingly open
check valve 130 into brake circuit 120, 122 until plunger piston
124 has finally reached its outer end stop. In order to thereby
prevent a buildup of a brake pressure in brake circuits 120, 122,
circuit separating valves 136 are thereby activated in such a way
that the pressure medium delivered by pressure generator 114 flows
through them and through master brake cylinder 118 into at least
one of the two chambers 146, 148 of reservoir 144 assigned to one
of the two brake circuits 120, 122.
[0023] Check valves 130 are now closed by electronic control unit
142 in order to temporarily decouple pressure generator 114 from
brake circuits 120, 122 and plunger piston 124 moves back in the
direction of its inner stop due to the reversal of its drive
direction. Plunger piston 124 thereby sucks pressure medium out of
assigned third chamber 150 of reservoir 144 into cylinder 128 via a
line 154 controlled by a return valve 152. When the plunger piston
has arrived at its inner stop, check valves 130 open again, the
drive direction of plunger piston 124 is reversed again, plunger
piston 124 travels across the orifice cross section of line 154 and
consequently pumps another quantity of pressure medium into at
least one of chambers 146, 148 of reservoir 144 assigned to one of
brake circuits 120, 122. This process is repeated until third
chamber 150 of reservoir 144 assigned to pressure generator 114 has
reached its minimum fill level and the fill level monitoring device
responds. The number of necessary actuating cycles or the actuation
duration of pressure generator 114 until chamber 150 of reservoir
144 is emptied to the minimum fill level may be ascertained from
the known geometric design variables, such as the volume of
pressure medium displaced per plunger stroke; the volume of chamber
150 assigned to pressure generator 114; the minimum fill level
volume of chamber 150; the speed of plunger piston 124 in the
extension or retraction direction, etc., and predefined by
electronic control unit 142. During this period, the signal of the
fill level monitoring device is thereupon monitored in electronic
control unit 142, whether a continuous signal change takes place or
a signal jump occurs, as is to be expected by a response of the
fill level monitoring device toward the end of the period. If yes,
then a proper function of the fill level monitoring device may be
inferred and a warning signal to the driver is suppressed. In this
case, the method is repeated at a later point in time, preferably
after a longer idle period of the vehicle or, for example, each
time that a renewed startup of the vehicle drive is carried
out.
[0024] If, in contrast, no continuous or steady signal change takes
place, or no signal jump is determinable in the observation period,
this indicates a malfunction of the fill level monitoring device
and a corresponding warning signal is emitted to the driver by
control unit 142. A suitable warning signal may be a visual, an
acoustic, and/or an haptic signal.
[0025] The recycled volume of pressure medium may automatically
flow back via the equalizing opening between at least one pressure
medium chamber 146, 148 of brake circuit 120, 122 and pressure
medium chamber 150 of pressure generator 114 until the pressure
medium levels in chambers 146 through 150 have equalized again.
With knowledge of the cross-sectional dimensions of this pressure
medium connection or the volume flow through the pressure medium
connection, conclusions about the quality of the pressure medium
may be derived from the time necessary for this, for example, about
its viscosity, its temperature, and/or the degree of contamination.
If necessary, a recommendation for exchanging the pressure medium
may be emitted to the driver by electronic control unit 142. The
time detected thereby is that time that elapses following the end
of the observation period until the fill level monitoring device
emits the signal indicated before the observation period.
[0026] FIG. 2 shows a schematically simple pressure medium circuit
210 having a pressure medium reservoir 212, whose reservoir space
is divided into two pressure medium chambers 214, 216 that
communicate with one another. The two pressure medium chambers 214,
216 are separated from one another, for this purpose, with the aid
of a partition 218, which has an equalizing opening 220 with a
predefined opening cross section at the end facing the bottom of
pressure medium reservoir 212. The two pressure medium chambers
214, 216 are differently designed with respect to their volumes,
the smaller of the two pressure medium chambers 214 being equipped
with a fill level monitoring device 222. This fill level monitoring
device 222 is, by way of example, a float gauge 224, equipped with
a magnet, which is guided along a sensor element 226. A switch
contact 228 is situated, for example, at sensor element 226 at a
point in the interior of pressure medium chamber 214, which marks a
minimum fill level of pressure medium reservoir 212. The fill level
of pressure medium reservoir 212 should not drop below this minimum
fill level.
[0027] However, if this case occurs, then the magnet carried by
float gauge 224 effectuates, depending on the configuration of
switch contact 228, that two contacts close or an existing
connection between two contacts is interrupted. These types of
switch contacts 228 are also known as reed contacts. Alternatively
to switch contacts 228, float gauge 224 may also be used to actuate
a potentiometer fixed at sensor element 226, at which different
resistance values are set by float gauge 224 depending on the fill
level of pressure medium chamber 214, 216. Fill level changes thus
effectuate a continuous or steady change of the output signal of
sensor element 226.
[0028] An electronic control unit 230 is additionally present,
which detects and evaluates the respective output signal of sensor
element 226.
[0029] Outside of pressure medium reservoir 212, the two pressure
medium chambers 214, 216 are coupled via a pressure medium
connection 232. A pressure medium delivery unit 234, which is able
to deliver pressure medium from the first, smaller pressure medium
chamber 214 into the second, larger pressure medium chamber 216 of
pressure medium reservoir 212, is located in this pressure medium
connection 232 in order to thus lower the fill level in first
pressure medium chamber 214.
[0030] FIG. 3 illustrates the method again, already explained in
connection with FIGS. 1 and 2, with the aid of a flow chart.
[0031] It is initially established in a first step 310 of this
method whether the pressure generator of the hydraulic circuit is
electronically activated or is not in use. If the pressure
generator is in use, then the method is ended according to path 312
and restarted at a later time.
[0032] If the pressure generator is not active, then the output of
a triggering signal to a drive motor of the pressure generator and
thus its startup is carried out by an electronic control unit in
second step 314. The triggering signal is emitted for a
predefinable period, this period being determined by the duration
which the pressure generator requires in order to lower the fill
level in the first pressure medium chamber of the reservoir to a
minimum fill level. It is accordingly dependent on the present
pressure medium volume in the chamber of the pressure medium
reservoir, on the minimum pressure medium volume, and on the
delivery quantity of the pressure generator per time unit, and thus
ultimately on the viscosity of the pressure medium, and is, due to
the known geometric design of the pressure generator and the
pressure medium reservoir, determinable by the line cross section
or the ambient temperature and/or predefinable by the electronic
control unit.
[0033] During the period of an actuation of the pressure generator,
a signal check of the fill level monitoring device (position 316)
is carried out in an electronic control unit. It is thereby checked
whether the signal steadily changes or if a signal jump takes place
toward the end of the observation period. If one of these events
occurs, then a proper operating state of the fill level monitoring
device is assumed and the emission of a warning signal to the
driver is suppressed by the electronic control unit. The method is
thus ended and is restarted again (position 318) at a later point
in time.
[0034] However, if the signal profile does not correspond to these
expectations, a malfunction of the fill level monitoring device is
present and, according to position 320, a warning signal,
preferably an acoustic, visual, and/or haptic warning signal is
emitted to the driver.
[0035] In an advantageous embodiment, the described method is
regularly carried out, for example, after longer idle times of a
vehicle or during each new startup of a drive of the vehicle.
[0036] In a method phase parallel to this method phase, the output
signal of the fill level monitoring device is detected at the point
in time before the electronic triggering of the drive motor of the
pressure generator (position 322).
[0037] After the expiration of the period of an actuation of the
pressure generator to lower the fill level in the pressure medium
chamber to the minimum value, the elapsing time is measured
(position 324) until the fill level monitoring device displays this
output signal again. This period thus indicates how long it takes
until the pressure medium levels in the at least two pressure
medium chambers of a reservoir have again harmonized with one
another. By knowing the ambient temperature or the pressure medium
viscosity in the new state and the flow cross section of the
equalizing opening in the partition between the pressure medium
chambers of the reservoir, conclusions about the quality of the
pressure medium may be drawn by the electronic control unit from
the time duration (position 326), the instantaneous viscosity, its
water content or its contamination, etc. being understood as the
quality of the pressure medium. If necessary, a recommendation for
exchanging the pressure medium may be output by the electronic
control unit (position 328). Otherwise, a recommendation of this
type is suppressed and this quality check of the pressure medium is
restarted at a later point in time. The established quality of the
pressure medium may be considered by electronic control unit 142
during the calculation of control signals for setting a brake
pressure in brake circuits 120, 122 by pressure generator 114 and
valves 132, 134, shown in FIG. 1.
[0038] Changes or supplements beyond the described exemplary
embodiment of the method underlying the present invention are
naturally possible without departing from the basic aspects of the
present invention.
* * * * *